A Clinico-microbiological Study of Diabetic Foot Ulcers in an Indian Tertiary Care Hospital

RAVISEKHAR GADEPALLI MSC 2 BENU DHAWAN 2 VISHNUBHATLA SREENIVAS PHD 1 ARTI KAPIL 2 A.C. AMMINI DM 0 RAMA CHAUDHRY 2 0 Department of Endocrinology, All India Institute of Medical Sciences , New Delhi , India. Microbiology, All India Institute of Medical Sciences , New Delhi, 110029 , India 1 Department of Biostatistics, All India Institute of Medical Sciences , New Delhi , India; and the 2 Department of Microbiology, All India Institute of Medical Sciences , New Delhi , India; the OBJECTIVE - To determine the microbiological profile and antibiotic susceptibility patterns of organisms isolated from diabetic foot ulcers. Also, to assess potential risk factors for infection of ulcers with multidrug-resistant organisms (MDROs) and the outcome of these infections. RESEARCH DESIGN AND METHODS - Pus samples for bacterial culture were collected from 80 patients admitted with diabetic foot infections. All patients had ulcers with Wagner's grade 3-5. Fifty patients (62.5%) had coexisting osteomyelitis. Gram-negative bacilli were tested for extended spectrum -lactamase (ESBL) production by double disc diffusion method. Staphylococcal isolates were tested for susceptibility to oxacillin by screen agar method, disc diffusion, and mec A- based PCR. Potential risk factors for MDRO-positive samples were explored. RESULTS - Gram-negative aerobes were most frequently isolated (51.4%), followed by gram-positive aerobes and anaerobes (33.3 and 15.3%, respectively). Seventy-two percent of patients were positive for MDROs. ESBL production and methicillin resistance was noted in 44.7 and 56.0% of bacterial isolates, respectively. MDRO-positive status was associated with presence of neuropathy (P 0.03), osteomyelitis (P 0.01), and ulcer size 4 cm 2 (P 0.001) but not with patient characteristics, ulcer type and duration, or duration of hospital stay. MDRO-infected patients had poor glycemic control (P 0.01) and had to be surgically treated more often (P 0.01). CONCLUSIONS - Infection with MDROs is common in diabetic foot ulcers and is associated with inadequate glycemic control and increased requirement for surgical treatment. There is a need for continuous surveillance of resistant bacteria to provide the basis for empirical therapy and reduce the risk of complications. - W are a major medical, social, and orldwide, diabetic foot lesions economic problem and are the leading cause of hospitalization for patients with diabetes. Infectious agents are associated with amputation of the infected foot if not treated promptly. Proper management of these infections requires appropriate antibiotic selection based on culture and antimicrobial susceptibility results; however, initial management comprises empirical antimicrobial therapy, which is often based on susceptibility data extrapolated from studies performed on general clinical isolates (1). Several studies found methicillin-resistant Staphylococcus aureus (MRSA) in as many as 1530% of diabetic wounds (13). Infection with multidrug-resistant organisms (MDROs) may increase the duration of hospital stay and cost of management and may cause additional morbidity and mortality (4). Although increasing antimicrobial resistance is a pertinent problem in India, there is paucity of data on the frequency of MDRO infections and the outcome of such infections among diabetic foot ulcers in this region. The aim of this study was to determine the microbiological and antimicrobial susceptibility profile of organisms isolated from patients with diabetic foot ulcers. The risk factors for infection of ulcers with MDROs and the outcome of these infections were also studied. RESEARCH DESIGN AND METHODS Eighty diabetic patients with clinically infected foot ulcers admitted to the endocrinology ward at the All India Institute of Medical Sciences over a period of 2 years were studied. Ulcers were graded using the Wagner classification (5). Age, sex, type and duration of diabetes, glycemic control during the hospital stay, presence of retinopathy, nephropathy (creatinine 150 mol/l or presence of micro- or macroalbuminuria), neuropathy (absence of perception of the Semmes-Weinstein monofilament at 2 of 10 standardized plantar sites on either foot), peripheral vascular disease (ischemic symptoms and intermittent claudication or rest pain, with or without absence of pedal pulses), duration and size of ulcer, clinical outcome, and duration of hospital stay were noted on each patient. Clinical assessment for signs of infection (swelling, exudate, surrounding cellulitis, odor, tissue necrosis, crepitation, and pyrexia) was made. Ulcer size was determined by multiplying the longest and widest diameters and expressed in centimeters squared. Osteomyelitis was diagnosed on suggestive changes in the radiographs and bone scans. All cases were monitored until discharge from the hospital. Written consent was obtained from all subjects, and clearance was obtained from the institutes ethics committee. Microbiological methods Culture specimens were obtained at the time of admission, after the surface of the wound had been washed vigorously by saline, and followed by debridement of superficial exudates. Specimens were obtained by scraping the ulcer base or the deep portion of the wound edge with a sterile curette. The soft tissue specimens were promptly sent to the laboratory and processed for aerobic and anaerobic bacteria. Standard methods for isolation and identification of aerobic and anaerobic bacteria were used (6,7). Susceptibility testing Anti-microbial susceptibility testing of aerobic isolates was performed by the standard disc diffusion method as recommended by the National Committee for Clinical Laboratory Standards (8). All anaerobic isolates were tested for susceptibility to metronidazole and amoxicillin/ clavulanate by microbroth dilution test (9). Gram-negative bacilli were tested for extended spectrum -lactamase (ESBL) production by a double disc diffusion method, and Staphylococcus species were tested for methicillin resistance by using 1-g oxacillin disc and oxacillin screen agar (6 g/ml) recommended by the National Committee for Clinical Laboratory Standards (8). A vancomycin screen agar (6 g/ml) was also used to detect vancomycin intermediate isolates of Staphylococci. Confirmation of methicillin resistance was done by mec Abased PCR (10). MDROs, the primary study variable, w e r e d e fi n e d a s M R S A , b a c t e r i a producing (ESBL) (4), and methicillinresistant coagulase-negative staphylococci (11). Antibiotic treatment Intravenous empirical antibiotic therapy of amoxicillin-clavulanate combination (1.2 g i.v. every 8 h) was started at admission for all the patients. This was switched to oral administration (625 mg p.o. every 8 h). Metronidazole (500 mg i.v. every 8 h) was added to the drug regimen if cellulitis or gangrene was also present. Antibiotics were adapted based on the results of anti-m (...truncated)